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Appendix If.

heoretical statement of a non-condensing engine, where B is back
pressure of atmosphere.

P. 633. High - speed Engines.—These cannot be dis-
missed without mentioning two important examples.

The Willans Central-valve Engine has shewn exceptional
economy. Fig. 855 is a section through a compound type, where

A is the throttle valve controlled b^ a governor G, B the steam
chest, c the high-pressure and E the low-pressure cylinders, i> the
intermediate receiver, F the exhaust chamber, H the air cylinders,
and j the slide valve with piston trunk K. The eccentric being
on the crank pin, j and K move relatively by the amount of
eccentric travel, and ttie cranks are 180° apart. Steam
from B to c by the trunk, then similarly to D, E, and F ; but work
is only done on the down stroke, the pistons being In equilibrium